ExperimentalA unique identifier for the thought message.
OptionalcontentComplete replacement content for this thought message.
Optional_The _meta property is reserved by ACP to allow clients and agents to attach additional
metadata to their interactions. Implementations MUST NOT make assumptions about values at
these keys. Omitted means no metadata update; null is an explicit clear signal.
See protocol docs: Extensibility
An agent thought or reasoning message upsert.
Only [
AgentThought::message_id] is required.contenthas patch semantics: an omitted field leaves existing thought content unchanged,nullclears the value, and a concrete array replaces the previous value. For a newmessageId, omitted fields use client defaults.contentis replaced as a whole array; send[]ornullto clear it.Message updates and chunks are applied in the order they are received. When an
agent_thoughtupdate includescontent, that array replaces any content previously accumulated for the thought, including content from earlier chunks. Later chunks with the samemessageIdappend to the current content.